1. Making Proteins: Translation
Lecture #20
Honors Biology
Ms. Day

2. mRNA  polypeptide (protein)
REVIEW… Translation
mRNA  polypeptide (protein)

3. Brings message from DNA (DNA instructions) to ribosome to make protein
Type of RNA
Function Job
Picture
mRNA
(messenger RNA)
Brings message from DNA (DNA instructions) to ribosome to make protein
tRNA
(transfer RNA)
Transfers/moves amino acids to ribosomes
rRNA
(ribosomal RNA)
Makes up ribosomes along with proteins

4. tRNA
A cell translates mRNA message into protein with help from transfer RNA (tRNA)
Each carries a
specific amino acid
“t” shape
Carries amino acids
Matches codons to
anticodons

5. tRNA delivers amino acids to ribosomes
Amino acid comes on and off! OR

6. Ribosomes
Help bind tRNA anticodons with mRNA codons during translation
Anticodon (tRNA) = codon (mRNA)

7. REVIEW…The Genetic Code
It’s a table used that TRANSLATES RNA nucleotides called CODONS (or mRNA “letters”) into one of the 20 amino acids
3 letter mRNA “word” = 1 amino acid
There are 4 different RNA “letters” that can be used
A, U, C, and G

8. THE GENETIC CODE

9. (with codons…codes for aa)
AMINO ACIDS
tRNA
(with anticodons)
mRNA
(with codons…codes for aa)

10. Ribosomes There are 2 ribosomal subunits
Constructed of proteins and ribosomal RNA or rRNA

11. Building a Polypeptide
Translation can be divided into 3 phases
Initiation
Elongation
Termination

12. Initiation of Translation
initiation stage brings together
mRNA
tRNA bearing 1st amino acid (“start”) called MET
2 subunits of a ribosome come together

13. Translation initiation complex
Large
ribosomal
subunit
Initiator tRNA
mRNA
mRNA binding site
Small
Translation initiation complex
GDP
GTP
Start codon
Met U A C G 3 5
Figure 17.17

14. Elongation
Amino acids are added one by one to the preceding amino acid
Peptide bonds are formed
Amino acid

16. Termination of Translation
When the ribosome reaches a stop codon on the mRNA
There are 3 stop codons
UAA, UAG, and UGA
Release factor (protein) binds to stop codon (NOT tRNA)  polypeptide released

17. Termination of Translation
Release
factor
Free
polypeptide
Stop codon
(UAG, UAA, or UGA) 5 3

18. Phe tRNA Anticodon 5 3 Amino acids “EMPTY” tRNA tRNA with amino acid
TRANSCRIPTION
TRANSLATION
DNA
mRNA
Ribosome
Polypeptide
Amino
acids
tRNA with
amino acid
attached
tRNA
Anticodon
Trp
Phe
Gly A G C U
Codons 5 3
“EMPTY”
tRNA
Figure 17.13

19. Polypeptide  3D Protein
Primary Structure
Amino acids is a row (LINEAR)
Secondary Structure
Amino Acids BEND and FOLD towards each other
Tertiary Structure
Amino acids BIND to each other
3D shape made
Quartnary structure (only some)
2 or more polypeptides BIND to each other

20. 1 2 4 3

21. Translation (Protein Synthesis) Animation